Self-cleaning litter box

ABSTRACT

A self-cleaning litter box for cats employs a comb drive to drive a comb through litter to remove waste from the litter. A sensor for detecting the presence of an obstruction is coupled to the comb drive and stops the comb drive upon detecting an obstruction. A manual mode selector switch and an actuating switch are provided to manually activate the cleaning of the litter box at a time deemed appropriate by the cat owner. A foot pedal unit may be provided for semi-automatic use. A removable tray for cat litter may be provided. The tray may be disposable. A pivotable ramp facilitates ingress to, and egress from, the litter box. The ramp may be carpeted. A tray receives the litter box and a hood encloses the litter box to provide privacy.

The present invention is directed to litter boxes and particularly toself-cleaning litter boxes for cats.

BACKGROUND

Cats are usually trained to use a litter box for elimination of bothliquid and solid wastes. A cat litter box is normally made of plastic orlike material so that a cat's urine will not leak through the box. Othercat litter boxes have been proposed, as in the construction described inU.S. Pat. No. 5,249,549 (Rockaitis), in which the litter box is made ofa material that absorbs liquid but does not permit it to leach throughto the exterior of the box. The litter used in boxes of this kind may beone of any number of particulate litter or other materials that absorbmoisture from the waste of the cat. The material may also suppress odorfrom cat waste. Some forms of cat litter form clumps when wet. Usually,a cat will bury its solid waste in the litter material in the box.

Most cat owners take appropriate action to discard the litter from a catlitter box after an appreciable period of time, often several days. Onthe other hand, even before the litter has been thoroughly saturatedwith waste from the cat or cats that use it, a cat may be inclined topush some of the litter out of the box, particularly if the odor isstrong. In any event, the person using a cat litter box may find thetask of emptying the cat litter to be unpleasant. Thus, a number ofdevices have been proposed for cleaning cat litter boxes. Such devicesare disclosed in U.S. Pat. Nos. 4,096,827 (Cotter), 4,117,804 (Moore etal.), 4,190,525 (Menzel), 4,325,325 (Larter), 4,325,822 (Miller),5,048,465 (Carlisi), 5,226,388 (McDaniel), and 5,477,812 (Waters).

The self-cleaning cat litter box disclosed in the Carlisi patentutilizes a rake or comb that is normally maintained in a storageposition at one end of the litter chamber. At predetermined intervals,the comb is moved through the litter, from the rake storage end of thechamber to the opposite end, which constitutes a discharge end for thechamber. At the discharge end of the chamber the rake moves up out ofthe litter and discharges any clumps collected by the comb into adisposal receptacle. Unfortunately, because cats are not consistent intheir elimination habits, such periodic cleaning may be too frequent, ornot frequent enough.

The Waters patent describes a system for moving a comb or rake throughthe litter responsive to entry and exit of the cat from the litter box.In addition, Waters provides an improved disposal receptacle and alarmsto report an insufficient litter supply and a fill disposal receptacle.The entire disclosure of the Waters '812 patent is incorporated hereinby reference.

Despite the advances made by these prior art patents, there remainsseveral deficiencies in self-cleaning litter boxes. First, if the cat ispresent in the litter box while the rake or comb is moving, the cat maybe startled to move suddenly and spill the contents of the litter boxor, the cat could be caught by the mechanism. Second, devices thatrequire the passage of time or the activity of a cat to initiate therake drive mechanism do not allow for use of the rake at other times.Third, easy access is needed to aid cats in entering and exiting thelitter box. The open boxes allow litter to be spilled out and do notprovide cover for cats that may desire privacy.

SUMMARY

The present invention alleviates to a great extent the deficiencies ofthe prior art by providing a litter box having a housing defining anupwardly open litter chamber for receiving cat litter, a comb disposedin the litter chamber, a carriage supporting the comb, and a comb drivefor driving the comb between a storage position and a dischargeposition. The comb drive includes a reversible drive motor mounted onthe carriage. A reverse sensor is coupled to the carriage. The reversesensor is coupled to a first surface of the carriage and the sensorprovides a shut-off signal to the comb drive when the sensor detectsthat the carriage has contacted a cat, or other obstruction, whilemoving between the storage position and the discharge position.According to one aspect of the invention, the reverse sensor includes aswitch electronically coupled to the drive motor for providing theshut-off signal to the comb drive in the closed position. In oneembodiment of the invention, the reverse sensor is a leaf switch.

In another aspect of the invention, the litter box has a mode selectorswitch. The switch may have a manual operation selecting position and anautomatic operation selecting position. In addition, a manual operationswitch may be electrically connected to the mode selector switch.According to another aspect of the invention, the comb drive drives thecomb between a storage position and a discharge position in response toactuation of the manual operation switch when the mode selector switchis in the manual operation selecting position.

In yet another embodiment of the invention, a rectangular tray has sidewalls and a bottom wall that cooperate to define a housing-receivingregion. Hood supports are coupled to the rectangular tray. A hood iscoupled to the supports. The hood includes an opening for a cat to enteror exit the litter box. According to another aspect of the invention, ahousing access ramp is pivotally connected to the housing, preferably atthe opening.

In still another embodiment of the invention, the litter chamberincludes a removable litter tray for receiving the cat litter.

The present invention may also be provided with means for ensuring thatthe comb stops when it strikes a cat while moving between the storageand discharge positions. By stopping the comb, the situation in which acat is pinned between the comb and a wall is prevented.

The invention provides a manual cleaning mode that allows the cat ownerto initiate the waste removal upon the activation of a switch. Thismechanism would allow the cat owner to clean the waste out of the litterbox at a time deemed appropriate by the cat owner.

The invention also provides an enclosure for a self-cleaning litter boxto provide privacy for the cat. The enclosure could also be used toprevent litter from being spilled out of the box.

Other features and advantages of the present invention will be readilyapparent from the following description and drawings which illustratepreferred embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an automated self-cleaning litter boxfor use by a cat, constructed in accordance with a preferred embodimentof the invention, showing the litter box in a waiting condition with thecomb at the storage position. The dress panels have been removed forclarity to expose the internal structure.

FIG. 2 is a perspective view of the litter box of FIG. 1 in anintermediate condition with the comb traversing the litter box betweenthe storage position and the discharge position.

FIG. 3 is a perspective view of the litter box of FIG. 1 in a dischargecondition with the comb in the discharge position.

FIG. 4 is a transverse sectional view taken along line 4--4 of FIG. 2and includes the dress panels.

FIG. 5 is a side view, partially broken away, of another litter boxconstructed in accordance with the invention.

FIG. 6 is a plan view of the litter box of FIG. 5. FIG. 7 is an endview, as seen from the storage end, of the litter box of FIG. 5.

FIG. 8 is a front view of a locking tab and a locking projection,according to a preferred embodiment of the present invention, forretaining a removable litter tray in the litter box of FIG. 5.

FIG. 9 is a partially broken away side view of the locking tab of FIG. 8engaging a locking notch formed on the locking projection.

FIG. 10 is a partially broken away side view of the locking tab of FIG.8 illustrating the locking tab in a depressed position to disengage thelocking tab from the locking notch.

FIG. 11 is a top view of a rotating tray lock for retaining theremovable tray in the litter box of FIG. 5.

FIG. 12 is a side view of the rotating tray lock of FIG. 11.

FIG. 13 illustrates the rotating lock of FIG. 11 in an unlockingposition.

FIG. 14 illustrates the rotating lock of FIG. 11 in a locking position.

FIG. 15 is a partial section view along line 15--15 of FIG. 13, throughthe litter box and removable tray of FIG. 5 illustrating a rotating traylock in relation to the litter box and removable tray.

FIGS. 16-18 are partial perspective views illustrating the sequence ofremoving a removable litter tray from the litter box of FIG. 5.

FIG. 19 illustrates a reverse sensing leaf switch, according to apreferred embodiment of the present invention, in an open-circuitconfiguration.

FIG. 20 illustrates the leaf switch of FIG. 19 in a closed-circuitconfiguration.

FIG. 21 is a block diagram of the drive and control for the litter boxof FIG. 5.

FIG. 22 is a side view of the self-cleaning litter box of FIG. 5,including a manual operation foot switch.

FIG. 23 is a flow chart for operation of the cat litter box of FIG. 5.

FIG. 24 is a flow chart illustrating optional modes of operation for thecontrols of the automated self-cleaning cat litter box of FIG. 5.

FIG. 25 is a perspective view illustrating a hood supporting structure,according to a preferred embodiment of the invention, including a trayand hood supports.

FIG. 26 illustrates the tray of FIG. 25 with a hood disposed over thehood supports.

FIG. 27 illustrates an end portion of a hood support of FIG. 25 engagingan opening formed in a sidewall of the tray; and

FIG. 28 illustrates a self-cleaning litter box disposed in the tray ofFIG. 25.

FIG. 29 is a sectional view of the waste receptacle of the Self-CleaningLitter Box illustrated in FIG. 1 with a lid of the receptacle in aclosed position.

DESCRIPTION OF PREFERRED EMBODIMENTS

FIGS. 1-4 illustrate a self-cleaning litter box 20 that includes a comb43 that rakes clumps of litter 71 into a waste receptacle 68. The comb43 moves from a storage position, shown in FIG. 1 to a dischargeposition, shown in FIG. 3. As the comb 43 approaches the dischargeposition, the lid 69 of the waste receptacle 68 opens to allow clumps oflitter 71 to enter the receptacle. After dumping the clumps of litter 71into the receptacle 71, the comb 43 automatically reverses direction toreturn to the storage position. A sensor 400, shown schematically inFIGS. 1-4, detects the presence of a cat or other obstruction, andautomatically stops the comb and reverses its direction of travel.

FIGS. 1-4 illustrate a litter box 20 having a pan-shaped housing 21. Thehousing 21 has a near side wall 22, a far side wall 23, and a dischargeend wall 24 joining the sidewalls 22, 23 at one end of the litter box20. The litter box 20 also has a comb storage end wall 25 connecting thesidewalls 22, 23 at the other end of the litter box 20. The bottom ofthe litter box 20 is identified by reference numeral 26. The fill levelto which the box 20 is usually filled with cat litter is shown by litterlevel line 38 (dashed line). The litter level line 38 may be afforded bya continuous or interrupted ridge in the interior of the housing 21.Thus, the litter box 20 has a discharge end 28 at one end and a combstorage end 29 at the opposite end. The sidewalls 22, 23, end walls 24,25 and bottom 26 to the box 20 are preferably formed in a moldingoperation that produces the complete housing 21.

A comb shaft 41 extends across the litter box 20 between two side tracks32, 33. There are four hangers 42 journalled on and depending from theshaft 41. Three of the hangers 42 appear in FIGS. 1-3. The fourth hanger42 can be seen in FIG. 4. A comb or rake 43 is suspended from thehangers 42 and includes a plurality of tines 44. In FIG. 1, whichillustrates a waiting, or storage, condition, the comb 43 is located atthe comb storage end 29 of the litter box 20, and the tines 44 areelevated above the litter fill level 38. In FIG. 2, which illustrates anintermediate condition, the comb 43 is traversing the litter box 20 fromthe storage end 29 to the discharge end 28, and the lower ends of thetines 44 project down into the litter in the box 20, close to the bottom26 of the box 20, also shown in FIG. 4. In FIG. 3, the comb 43 is shownnear the end of its raking stroke at the discharge end 28 of the litterbox 20. At the discharge end 28 of the litter box 20, the tines 44 ofthe comb 43 again move upwardly out of the litter.

An elongated near side track or path member 32 extends along the top ofthe near side wall 22 of housing 21. Track member 32 includes amultiplicity of equally spaced apertures 31. Apertures 31 extend throughan inclined portion 34 of rack 32 at the discharge end 28 of litter box20; they also extend through a more steeply inclined portion 36 of rack32 at the comb storage end 29 of the litter box 20. This trackconstruction is repeated on the opposite side of housing 21. Thus, anelongated track member 33 projects horizontally from the vertical sidewall 23. Track member 33 includes a multiplicity of equally spacedapertures or perforations 39. The pattern of apertures extends along aninclined portion 35 of the track member 33 at the discharge end 28 oflitter box 20. It also extends along a more steeply inclined portion 37of the track 33 located at the comb storage end 29 of the litter box 20.

A first main guide wheel 52 is affixed to the near end of shaft 41.Guide wheel 52 includes a plurality of radially projecting guide pins orteeth 51 engageable in the apertures 31 of track member 32 and itsextensions 34 and 36. At the other end of shaft 41 there is a similarmain guide wheel 53. The radial projections 54 on guide wheel 53 areengageable in the apertures 39 of track member 33 and its extensions 35and 37. Guide wheels 52 and 53 cause the ends of shaft 41 to move alongtracks 32 and 33, based on rotation of shaft 41, from the storageposition of FIG. 1 through the intermediate position of FIG. 2 to thedischarge position of FIG. 3 and back to the FIG. 1 storage position.

In addition to the main guide wheels 52, 53 referred to above, the driveand guidance system of litter box 20 includes two auxiliary guide wheels64, 65, located on the near and far sides of the litter box 20,respectively, as seen in FIGS. 1-3. Auxiliary guide wheel 64 is mountedat the end of a lever 66 that projects from one of the hangers 42 usedto suspend comb 43 from shaft 41. Auxiliary guide wheel 64 rides alongtrack 32 throughout the length of that track, including its upwardlyinclined end sections 34 and 36. Similarly, the auxiliary guide wheel 65is mounted on a lever 67 and engages the other track member 33 and itsextensions 35, 37 (FIG. 4).

FIG. 5 illustrates an alternative track 231. In particular, the track231 includes an upper surface 235 spaced apart from a lower surface 237and a plurality of teeth 239 depending from the upper surface 235. Aguide wheel 253 for use with the track 231 includes a plurality of cogs254 for engaging the teeth 239. A secondary hub 241 extends outwardlytoward the side walls from the wheel 253 and is sized to cooperate withthe lower surface 237 to prevent the cogs 254 from disengaging from theteeth 239. Advantageously, the use of teeth 239 depending from the uppersurface 235 avoids the possibility of litter becoming lodged between theteeth 239 and blocking movement of the wheel 253.

The improved self-cleaning cat litter box 20, FIGS. 1-3, includes a combdrive that comprises a reversible electric motor 55 mounted on andconnected in driving relationship to the shaft 41 that supports comb 43;the final gear 57 of the gear train that connects motor 55 to shaft 41is the only gear that appears in the drawings. The motor 55 is energizedby batteries contained in a battery case 56. Motor 55 and the gear trainrepresented by gear 57, as well as battery case 56, are supported byshaft 41; in conjunction with the shaft, they constitute the carriage 45for the comb 43 in litter box 20. A reversing switch 58 is mounted onand electrically connected to motor 55. A lever 59 is mechanicallyconnected to reversing switch 58. Lever 59 has a limited pivotalmovement, from the position shown in FIG. 1 to the position illustratedin FIG. 2. A first switch actuation pin 61 is located adjacent the combstorage end 29 of litter box 20. A similar fixed switch actuation pin 62is positioned at the other end, the discharge end 28, of litter box 20.

A waste receptacle 68 is positioned immediately adjacent to thedischarge end 28 of the litter box 20. In FIGS. 1 and 2, waste clumps 71are indicated in the litter chamber; similar clumps 72 are shown, inFIGS. 1-3, as being already deposited in receptacle 68. Receptacle 68has a hinged lid 69 and a pair of indentations 63, 70 (FIG. 6). Theindentations 63, 70 are formed in the bottom of the receptacle 68 andreceive bosses 222, 223 (FIG. 29). The bosses 222, 223 retain the wastereceptacle 68 in position within the litter box 20. Waste receptacle 68and its lid 69 are preferably formed of a biodegradable material.Moreover, receptacle 68 should be transparent; alternatively, lid 69 maybe transparent or, of course, both may be transparent enough to permitthe user to visually check the level of waste and litter in thereceptacle 68. Lid 69 is engaged by a pin 75 on a lid lift lever 73 thatis pivotally secured to a vertical extension 27 of side wall 23. Thepivotal connection is indicated at 74. There need be no comparable lidlift mechanism 73-75 at the near side of the machine, though one couldbe provided if motor 55 and battery case 56 were mounted closer to thecenter of the litter box.

Waste receptacle 68 may be formed of plastic or other suitable material.The lid 69 for receptacle 68 is hinged to the receptacle as indicated at76. A hinge of the so-called "piano" type may be used, but other hingestructures are acceptable. Lid 69 may also be formed of plastic. On theother hand, receptacle 68 and its lid 69 may be fabricated of otherappropriate material. Preferably, receptacle 68 initially serves as acontainer for clean litter so that, once the receptacle 68 is ready tobe discarded, it can simply be removed and a new receptacle 68 put inplace after emptying clean litter from the new waste receptacle 68 intothe chamber afforded by housing 21.

A sensor may be used to determine whether or not the receptacle is full.In the embodiment of FIGS. 1-3, a sensor 243, preferably aphotodetector, is mounted on side wall 23 at a level indicative of afill receptacle. An appropriate light source 242 is mounted on side wall22 opposite photodetector 243. When the litter level rises in thereceptacle to block the light from the source 242, photodetector soundsan alarm, such as a buzzer, to alert the user.

Another sensor may be utilized to sense the exit of a cat from thelitter chamber afforded by housing 21. In the embodiment of FIGS. 1-3,there are two such sensors 82, 84, both mounted on wall 23 above thelitter fill line 38. Devices 82 and 84 may comprise conventional photodetectors, each receiving a light beam from a source (not shown). FIG. 4shows an appropriate light source 86 mounted on wall 22 above fill level38. Photodetector 82 (FIG. 4) is also located above fill level 38. Asingle light source located centrally along the length of wall 22 can beused or there may be two such light sources 86, one for each of thephoto detectors 82, 84.

As shown in FIGS. 5-7, a removable litter tray 300 is disposed in thelitter box 20 adjacent the bottom 26. The tray 300 includes a handleportion 306 and a tray portion 304. The tray portion 304 is filled withlitter to the fill line 38 as discussed above. The tray portion 304includes a distal end 305 and a proximal end 307 and is designed toslide through an opening 301 of the storage end wall 25. The side walls22, 23 of the housing 21 may contain rails, detent projections or othermechanisms (not shown) to ensure the sliding engagement of the trayportion 304 in the litter box bottom 326. The tray portion 304 is slidthrough the storage end wall 25 until the distal end 305 of the trayportion 304 comes into contact with the discharge end wall 24. When thetray portion 304 comes into contact with the discharge end wall 24, thehandle portion 306 of the removable litter tray 300 extends through thestorage end wall 25. In preferred embodiments, the corners and edges ofthe housing 21 and the removable tray 300 are rounded to facilitatecleaning as illustrated, for example, in FIGS. 4 and 7. Preferably, theapparatus 200 has no nooks, crannies or other small spaces of the typethat would permit litter or waste to slip out of or become lodged in theapparatus 200.

Other features are also illustrated in FIGS. 5-6. In particular, analternative lift mechanism 174 includes a lift plate 173, connected tothe litter box 20 by a hinge 176, and a pair of end walls 175, 177disposed orthogonally to the plane of the lift plate 173. Each end wall175, 177 includes a camming edge 179 operatively disposed to engage thecarriage 45 as the carriage moves to the discharge position. Preferably,the lift plate 173 includes a plurality of apertures 181 for receivingcomplementary tabs 183 formed on the lid 69 of the receptacle 68. Thetabs 183 fit in the apertures 181 with a friction fit to connect the lid69 to the lift plate 173. Thus, as the carriage 45 approaches thedischarge position, it engages the camming edges 179 and pivots the liftplate 173 about the hinge 176 to open the waste receptacle 68. Thefriction fit of the tabs 183 in the lift plate 173 allows the lid 69 tobe easily removed from the lift plate 173 to be disposed of with a fullwaste receptacle 68.

As shown in FIGS. 5 and 6, the apparatus 200 also has parallel sidewalls 201 on opposite lateral sides. The side walls 201 may be formed ofa suitable plastic material. The side walls 201 have top edges 202extending from the back to the front of the apparatus 200. The sidewalls 201 help prevent cat litter or other debris from being spilled outof the apparatus 200.

As illustrated in FIGS. 8-10, the handle portion 306 includes aresilient locking tab 302 formed therein. A locking projection 320extends downwardly from the outside surface 325 of the comb storage endwall 25 to a distal end 326. The locking projection 320 includes a frontwall 322 and a pair of sidewalls 324 extending from the edges of thefront wall 322 to define a U-shaped channel. The distal end of the frontwall 322 includes a semicircular opening 327 (FIG. 8), and the distalend of each sidewall 324 includes a notch 328, (FIGS. 9-10). The notches328 are disposed to engage the locking tab 302 when the tray portion 304is completely slid into the housing 21.

When the litter tray 300 is disposed in the litter box 20, the lockingtab 302 engages the notches 328 to retain the tray 300 in the litter box20. To remove the tray 300, a user inserts a finger into thesemicircular opening 327 and depresses the resilient locking tab 302,causing the tab 302 to disengage from the notches 328. Although alocking projection 320 and a locking tab 302 have been illustrated, itwill be appreciated that other latching mechanisms can be used. Thelocking tab 302 is preferred, however, because it is easy to operate andis readily formed integrally with the removable tray during the moldingprocess.

In addition to the locking tab 302, the litter box 20 includes a pair oftray locks 330, illustrated in FIGS. 11-15, disposed on the dischargeend wall 24. As shown in FIGS. 11-12, each tray lock 330 includes alocking disk 333 and a shaft 335 that projects from the bottom surfaceof the disk 333 and is offset from the center of the disk 333. Theshafts 335 include a groove 337 for receiving a circlip 338. The shafts335 are sized to extend through apertures 339 formed in the dischargeend wall 224, with the disks 333 cooperating with the circlip 330 toretain the tray locks 330 in position. Thus, tray locks 330 arerotatably connected to the discharge end wall 224. The apertures 339 arelocated on the end wall 224 so that the offset portion of the disk 333rotates between an unlocking position (FIG. 13), wherein the removabletray 304 is released for removal, and a locking position (FIG. 14). Inthe locking position, a portion of the disk 333 overlaps the distal end305 of the removable tray to prevent removal, as illustrated in phantomin FIG. 15. The tray locks 330 can be adapted to have grooves 341. Thegrooves 341 would be used to allow a tool 334, such as a screwdriver ora coin, to lock and unlock the tray locks 330. Other indicia 343 may beadded to indicate whether the tray locks 300 are in the locking orunlocking position.

As illustrated in FIG. 15, the removable tray 300 preferably includes abeveled edge 345 formed on the distal end 305, and the discharge endwall 224 includes a beveled step 347 formed to be complementary to thebeveled edge 345. The beveled edge 345 and step 347 cooperate to providea seam that resists litter intrusion.

To remove the litter tray 300, as illustrated in FIGS. 16-18, a userinserts a tool 334 into the tray locks 330 to rotate the tray locks 330in direction 332 (FIG. 16) to the unlocking position. Of course,different tray locks 330 can be used. For example, a sliding tray lockcould be used. Once both tray locks 330 are in the unlocking position,the user may depress the locking tab 302 (FIG. 17) to disengage the tab302 from the locking projection 320. Once disengaged, the tray 300 maybe removed from litter box 20 by pulling on the handle portion 306 inthe direction 336 (FIG. 18).

In the preferred embodiment of the present invention, as shownschematically in FIGS. 1-3 and in detail in FIGS. 19-20, a reversesensor 400 is coupled to a back side of the carriage 45 to avoid injuryto a cat in the event that the carriage makes contact with the catduring movement toward the storage position. It will be appreciated thata forward sensor can be used to avoid injury to a cat if the carriage 45contacts the cat during movement toward the discharge position. Thereverse sensor 400 includes a reverse sensing bar 402, an actuating bar408, and a leaf switch 410. The leaf switch 410 is connected to thecarriage 45 at a point adjacent the actuating bar 408. The reversesensing bar 402 is held in a flexible relationship with the carriage 45by first and second bar holders 404, 406 molded therein (FIG. 6). Thebar holders 404, 406 contain springs (not shown) to provide thisflexible relationship.

Referring to FIG. 19, the leaf switch 410 includes a base 420, aflexible leaf switch arm 426, a rigid leaf switch arm 422 and a leafswitch arm separator 424. The separator 424 prevents the contacts 423,425 from inadvertently making contact. The leaf switch arms 422, 426have leaf switch contacts 423, 425. The leaf switch arms 427, 429 mayalso include leaf switch contact protectors 427, 429, respectively, toprevent damage to the contacts 423, 425.

When the carriage 45 contacts a cat, or other obstruction, a force isapplied to the reverse sensing bar 402, and the force is transmitted tothe flexible leaf switch arm 426 by the actuating bar 408. The actuatingbar 408 pushes the leaf switch arm 422 to bend the arm 422 around theleaf switch arm separator 424, causing the leaf switch contact 425 totouch contact 423. The leaf switch 410 is closed, and an electricalconnection is maintained, while the contacts 423, 425 are in contactwith each other. When the leaf switch 410 is closed, a signal isgenerated to stop and reverse the motor 55 (described below).

The leaf switch 410 is resiliently biased toward its open position (thatis, the contacts 423, 425 are biased away from each other). The leafswitch 410 will be closed (as described above) when the sensing bar 402contacts the end wall 25 and the contact 425 of the flexible leaf switcharm 426 is forced into contact with the contact 423 of the rigid leafswitch arm 422.

Referring now to FIG. 21, motor 55 is energized from battery 56 througha pre-programmed micro-processor control 96. Although not shown in FIG.21, a conventional electrical power supply may alternatively be used toenergize the motor 55. Control 96 receives input signals from singlespace sensors 82, 84. Additional inputs to control 96 may be supplied bya mode select switch 91, a motor stall sensor 92, a battery voltagesensor 93, a home position sensor 94 for the comb 43, a reverse sensor400, and a manual operation switch 370.

The mode select switch 91 (FIG. 5) is a three position switch. The modeselect switch 91 is switchable between an automatic operation selectingposition, a manual operation selecting position and an off position. Themode select switch 91 allows a user to decide how the litter box 20 isto operate (manually, automatically, or not at all). No power issupplied to the litter box 20 when the mode select switch 91 is in theoff position. The mode select switch 91 provides an automatic operationinput and a manual operation input to the control 96. In the off modesno input is generated because all components, including the control 96,will not be functioning.

The motor stall sensor 92 determines whether the motor 55 is stalled. Ifthe motor 55 is started by the control 96, but becomes stalled, themotor stall sensor 92 will supply a motor stall input to the control 96.

The battery voltage sensor 93 determines whether there is a low batteryvoltage condition. If there is a low battery voltage condition, thebattery voltage sensor 93 supplies a low battery voltage condition inputto the control 96. The control 96 sends a signal to sound a buzzer 97when the low voltage input is received.

The home position sensor 94 for the comb 43 determines whether the comb43 has reached the "home" position. If the comb 43 has reached the"home" position, the home position sensor 94 supplies a "home" positioninput to the control 96. In response to the home position input, thecontrol 96 stops the motor 55.

A manual operation foot switch 370 (FIG. 22) allows a user to initiatemanual operation of the litter box 20 by closing the switch 370 if themode selector switch 91 is in the manual position. When the switch 370is closed, a manual operation switch activated input is sent to thecontrol 96.

Limit switches 95, 99 may be provided at the storage end 28 and at thedischarge end 29 of the litter box 20. One or more buzzers or otheralarm devices 97 are included in the circuit so that the cat owner canbe signaled when the litter box 20 is functional or when otherconditions occur, such as an insufficient litter supply in the box 20 ora fill waste receptacle 68 or low battery voltage.

If desired, the apparatus 200 may be provided with a shut-off timersystem (not illustrated). The shut-off timer system may be used todisable operation of the apparatus 200 for a predetermined period oftime, for example, six hours. Thus, for example, the apparatus 200 maybe disabled during the middle of the night, so that the apparatus 200does not disturb resting persons or other pets. A push button over-ridesystem (not illustrated) may be provided to manually initiate a rakingoperation when the apparatus 200 is otherwise disabled by the shut-offtimer system.

The motor stall sensor 92, battery voltage sensor 93, buzzer 97, andleaf switch 410 of reverse sensor 400 may all be packaged in the samehousing with the motor 55. Such packaging would be particularlyadvantageous by eliminating the need for long wiring runs.

The mode selector switch 91, home position sensor 94, limit switches 95,99 and manual operation switch 370 can be incorporated in the litter box20 in appropriate positions as desired. Home position sensor 94 may becoupled to or adjacent to the "home" position. For example, if the"home" position is determined to be the storage end 29, then the sensor94 should be located adjacent to the storage end wall 25. Limit switch95 can be positioned to be actuated by any part of the comb 43 or thecarriage 45. The limit switch 95 is disposed at the storage end 28 oflitter box 20 and is activated when the comb 43 or carriage 45 reachesthe storage end 28 of the litter box 20. The limit switch 99 is disposedat the discharge end 29 of litter box 20 and is activated when the comb43 or carriage 45 reaches the discharge end 29 of the litter box 20.Manual operation switch 370 can be positioned adjacent the mode selectswitch 91, the carriage 45 or any other desired location on the litterbox 20.

In operation, the comb 43 may initially be located at the comb storageend 29. In this condition, the comb shaft 41 is elevated, the guidewheels 52, 53 having ridden up the extensions 36, 37 of tracks 32, 33.The switch 58 and the lever 59 have engaged the pin 61; the motor 55 isshut off, but is set for forward movement. Removable tray 300 is filledwith litter, approximately to level 38. Photo detectors 82 and 84receive light beams from sources 86 on the near wall 22 of the litterbox (FIGS. 4 and 23). With no cat present in the litter box 20,reception of the light beams by photo detectors 82 and 84 is unimpeded.All other mechanisms are in the positions shown in FIG. 1. Lid 69 isclosed over the receptacle 68. The receptacle lid 69 is engaged by pin75 at the end of the lever 73, but remains closed because the lidopening lever 73 is inactive.

At this juncture, it may be assumed that a cat (not illustrated) entersthe litter box 20 for the purpose of elimination of either liquid orsolid waste. With some kinds of litter, the urine from the cat creates aclump in the litter with which the bottom portion of housing 21 isfilled. For solid elimination, the clump is formed by the waste itself.In either instance, the cat is likely to bury the waste or to cover itwith other litter, especially with respect to solid waste. Thus, clumps71 are produced by the cat, and those clumps are located at some levelin the litter above the bottom of the removable tray 300 (FIG. 23). Itis assumed that the box 20 has previously been used and that previouslydeposited waste clumps 72 are already present in the waste receptacle68.

While the cat is present in the litter box 20, the light beam to atleast one of the photo detectors 82 and 84 is cut off. Usually, bothlight beams are blocked. However, this does not initiate a self-cleaningoperation in the litter box 20. Subsequently, when the cat leaves thelitter box 20, the light beam or beams again impinge upon the photodetectors. Accordingly, an output signal from one or both cat sensors issupplied to control 96 (FIG. 21). At this point, however, there still isno actuation of a self-cleaning operation in the box 20 by the comb 43.The reason for the delay is that the cat might return to the litter box,deciding that its elimination activities have not been completed. Inthese circumstances, the light beams to one or both of the photodetectors 82, 84 are again cut off and the preset delay interval foractuation of a self-cleaning operation is not completed.

Ultimately, the cat leaves the litter box 20 for an interval long enoughto exceed the preset time delay that is set into control 96. That timeinterval is subject to substantial variation; a range of two to sevenminutes is usually desirable. The self-cleaning operation carried out bythe comb 43 should not be initiated while the cat is in the immediatevicinity because it is undesirable to cause the cat to have reason to beafraid of the litter box 20.

In a preferred embodiment, the operation of the self-cleaning litter box20 can be also be performed manually. Instead of waiting for thepredetermined delay period, as previously described, cleaning of thelitter box 20 may be initiated by the cat owner. Manual operation can beachieved by placing the mode select switch 91 (FIG. 5) into a manualoperation selecting position. With the mode select switch 91 in thisposition, inputs from the photo detectors 82, 84 do not initiate thepreset delay feature previously described. Instead, the control 96 looksfor an input from the manual operation switch 370.

FIG. 22 illustrates the use of a foot switch 372 as the manual operationswitch 370. The foot switch 372 is a normally open switch providing noinput to the control 96 when open. The foot switch 372 is closed andthus activated when a cat owner steps on it. The closing of the footswitch 372 provides an input to the control 96 causing the comb 43 torake the litter (described below). This may be desirable when the catowner wants to remove the waste from the litter box 20 at a time he orshe deems appropriate.

After the cat has left litter box 20 for a time exceeding the presetdelay interval in control 96 (automatic operation) or after the manualoperation switch 370 has been activated (in manual mode), motor 55 isenergized from battery 56, or a conventional power supply (not shown),through control 96. As a consequence, gear 57 and shaft 41 are rotatedin the direction of the arrow B in FIG. 1. The initial movement of thecomb carriage 45 (shaft 41, motor 55, and battery housing 56) isdownwardly along track extensions 36 and 37. In the course of thisdownward movement of comb 43, its tines 44 are pushed downwardly intothe litter in the bottom portion of housing 21, well below fill line 38.The bottoms of the tines 44, when this movement is completed, are quiteclose to the bottom of the removable tray 300, but preferably do notquite engage the bottom.

Motor 55 remains energized and shaft 41 continues to rotate in thedirection of arrow B. As a consequence, comb 43 is driven across thelitter chamber, from the storage end 29 to the discharge end 28, asindicated in FIG. 2 by arrow A. Reference may also be made to FIG. 4,where the position of the comb and its tines 44 are illustrated. As thecomb moves across the litter box 20, in the direction of arrow A, thetines 44 engage any clumps 71 present in the litter, whether generatedby the elimination of liquid or solid wastes by the cat. Comb 43 carriesthe clumps 71 toward the discharge position 28 at the far end of box 20,that is, to the right hand end of the litter box 20 as seen in FIGS. 1and 2. Comb 43 remains in a substantially erect position as shown inFIG. 2. It is prevented from rotating in the direction of arrow B by theengagement of auxiliary guide wheels 64, 65 with tracks 32, 33respectively. The forward motion of the comb 43 in the direction ofarrow A is effected by rotation of shaft 41 in the direction of arrow Band the engagement of guide wheels 52 and 53 and their pins 51 and 54 inthe apertures 31 and 39 of the two tracks 32 and 33 that define the combpath.

Ultimately, the comb 43 advances to a position where its main guidewheels 52 and 53 reach the upwardly inclined extension portions 34 and35 of tracks 32 and 33, respectively. Motor 55 is still energized; as aconsequence, the carriage 45 moves up the ramps or track extensions 34and 35 to the position shown in FIG. 3. During this upward movement ofcomb 43, lever 73 is engaged by the comb carriage 45 and is pivotedupwardly from the original position shown in FIGS. 1 and 2 to theelevated position shown in FIG. 3. As a consequence, due to theengagement of pin 75 with a slot or like guide 77 in receptacle cover69, cover 69 is moved to the open position shown in FIG. 3. When comb 43reaches the discharge position shown in FIG. 3, the additional clumps 71are discharged into receptacle 68 to join clumps 72 already presentthere.

When comb 43 reaches the position of FIG. 3, it actuates the limitswitch 99. The resulting output signal to control 96 (FIG. 21) reversesmotor 55 and the motor 55 starts to rotate the shaft 41 in the directionof arrow C, FIG. 3. Accordingly, the comb 43 is driven, by motor 55,back to its storage position illustrated in FIG. 1. In the process, thedischarge lever 73 is disengaged and drops back down to its originalposition, so that the lid 69 on receptacle 68 again closes. The wastefrom the litter box 20 is now totally enclosed in waste receptacle 68.

When comb 43 has finished its movement back to a point closely adjacentto the storage end wall 25, its two main guide wheels 52 and 53encounter the steeply inclined upward extensions 36, 37 of tracks 32,33. Motor 55 remains energized and pulls comb 43 and its shaft 41 up tothe position shown in FIG. 1. When the comb 43 reaches that position,switch 58 is actuated by pin 61 and sets motor 55 for subsequentoperation in the forward direction. When comb 43 reaches the end of itstravel, at the position shown in FIG. 1, the comb limit switch 95 (FIG.21) is actuated and a signal is supplied to control 96 to shut off themotor. A "home" sensor 94 may be provided for the same purpose. Usually,it is desirable to have both a home sensor 94 and a limit switch 95 (seeFIG. 21) to actuate the control 96 and make sure that the motor 55 isshut off with the comb 43 at the storage position 29 shown in FIG. 1.

In a preferred embodiment, a reverse sensor 400 (FIGS. 6 and 19-20) isutilized to make sure that the motor 55 is stopped and reversed when thecomb 43 strikes an object while returning to the storage position 29.The reverse sensor 400 is normally open and does not provide an input tothe control 96 while open. The reverse sensor 400 is closed when thereverse sensing bar 402 strikes an object forcing the actuating bar 408to close the leaf switch 410. When the reverse sensor 400 is closed, aninput is sent to the control 96 indicating that the motor 55 should bestopped and reversed, and that the movement of the comb 43 should bestopped and reversed.

FIG. 23 is a flow chart illustrating a subroutine programmed intocontrol 96 (FIG. 21) for a self-cleaning operation in the improvedlitter box 20. The flow chart starts with a command to comb litter 101supplied to the control 96. As a consequence, a set direction and startcommand is supplied to the motor 55 in stage 102 of the subroutine. Inthe next stage 103, if the motor 55 is stalled, that condition is sensedand an output command is received by the motor 55 (stage 105) to reversethe direction of the motor 55. Ordinarily, however, the motor 55 willnot be stalled and the next step (stage 104) is to determine whether thecomb 43 is at its end of travel. If not, the subroutine returns to stage103 and checks for a stalled motor 55. If the comb 43 is located at thedischarge end of its travel, an output signal is applied to reverse themotor 55 (step 105).

When the motor 55 has been reversed, the condition of the motor 55 isagain checked to see if it is stalled. If so, there is an output signalto stop the motor 55 (step 108). Ordinarily, however, the motor 55 willnot be stalled and an enabling signal is received (stage 107) to checkand see whether the comb 43 is in its "home" position. When comb 43reaches its "home" position, at storage end 29 of litter box 20, thereis an output signal sent to stop the motor 55 (stage 108) which directsthe subroutine to return to the beginning of the subroutine (stage 109).If the comb 43 has not reached the "home" position, the subroutineproceeds to stage 107A to determine if the reverse sensor 400 has beenactivated. If the reverse sensor 400 has not been activated, thesubroutine returns to stage 106 and checks for a stalled motor 55. Ifthe reverse sensor 400 has been activated, there is an output signal(stage 107A) to a stop motor (stage 108). The subroutine then returns tothe beginning (stage 109). This completes the subroutine of FIG. 23.

FIG. 24 illustrates a further subroutine that is also programmed intoprocessor control 96 (FIG. 21). The subroutine starts with a power-onstage 111 that may be initiated by an appropriate switch (for example,the mode select switch 91). Alternatively, the subroutine may start withinsertion of appropriate batteries into battery case 55 (FIGS. 1-3) orby plugging in a conventional power supply (not shown). The next stage112 in the subroutine is initialization of the control 96. In the nextsubroutine stage 113, the control 96 checks to determine whether themode select switch 91 of FIG. 21 is set for manual mode.

If the manual operation mode is selected, the control 96 checks todetermine if a manual operation switch 370 (FIG. 22) has been activated(stage 113A). The manual operation switch 370 is normally open andprovides a NO signal (stage 113A) when open. The manual operation switch370 is activated by the cat owner. When the manual operation switch 370has been activated, a comb litter procedure is initiated (stage 114). Ifthe manual operation switch 370 has not been activated, the subroutinereturns to the mode check at stage 113.

If the program is not set for manual mode, the subroutine checks for alow battery condition (stage 115). If a low battery voltage condition isascertained, the subroutine checks to see if the alarm mode is set(stage 116) and, if the alarm mode is set, the subroutine actuates analarm (stage 117) to produce a programmed output from buzzer 97 (FIG.21) that alerts the user that a change of batteries is required. Outputsgenerated in stages 116 and 117 may be fed back to stage 113 in thissubroutine in appropriate circumstances. If a conventional power supplyis used to energize the motor 55, the control 96 may be programmed toskip stages 115 to 117. Ordinarily, however, when the voltages of thebatteries are adequate, there is a NO output and the subroutinecontinues by checking for a full septic or waste receptacle 68 (stage118). Ordinarily, the receptacle 68 will not be full. If the receptacle68 is full, the subroutine returns to stage 113.

In normal circumstances, with adequate room in the receptacle 68, thesubroutine checks to see if any septic is present (stage 119). If septicis present, the subroutine checks to determine if the comb 43 is in the"home" position (stage 121). If the comb 43 is in the home position, thesubroutine checks for the presence of a cat in the litter box (stage122). If the comb is not in the home position, or if the cat is notpresent in the litter box, the subroutine returns to the mode check(stage 113) and begins again. If the cat is present in the litter box,the subroutine waits for the delay time to expire (stage 123) and thenexecutes a comb litter command (stage 124) and returns to the mode check(stage 113) and begins again.

Thus, the automated self-cleaning litter box 20 may be arranged so asnot to frighten or disturb a cat; the self-cleaning movement of the comb43 may not occur until there is a reasonable certainty that a cat usingthe litter box 20 has been gone for two to seven minutes, depending onthe delay set into the control 96, before the motor 55 is energized.Other sensors can be used instead of photo detectors 82 and 94. Forexample, infra-red sensors receiving radiation from an appropriateinfra-red source, or a strain gauge on pan bottom 26, may serve the samepurpose as the photo detectors of FIGS. 1-4.

The gear drive 57 that connects motor 55 to shaft 41 is not subject tofouling by the litter, which often includes powdery material that islikely to interfere with operation of other drive mechanisms such as aworm drive. Motor 55 should be sealed against dust and dirt, since itmust operate in an adverse environment. Litter box 20 is simple andeconomical in construction, but should afford an extended operating lifewith little or no attention apart from periodic replacement of thelitter and replacement of the batteries 56.

In a preferred embodiment of the present invention, as shown in FIGS. 5and 6, a durable ramp 350 is pivotally connected to the housing 21. Theramp 350 includes carpeting 352 and first and second pivot pins 354, 356molded to one end of the ramp 350. The carpeting 352 is mounted upon atop side of the ramp 350. The carpeting 352 is ribbed and made of afabric that will trap litter and provide suitable paw-cleaning andscratching-post functions for a cat utilizing the ramp 350. The ribbedcarpet 352 traps litter. The carpet 352 may be easily removed forcleaning.

In order for the ramp 350 to be connected to the housing 21, the twoside walls 22, 23 may include first and second pivot holes 360, 362 atthe discharge end 28 of the litter box 20. The ramp 350 is attached tothe housing 21 by placing the first pivot pin 354 and the second pivotpin 356 into pivot holes formed in the side walls 22, 23 of the litterbox 20. The carpeting 352 is facing up as depicted in FIG. 6 and willminimize litter tracking when the cat exits the litter box 20.

Another feature of a preferred embodiment of the present invention, asshown in FIGS. 25-28, includes a rectangular tray 500 having first andsecond side walls 504, 508, an end wall 506 connected between the sidewalls 504, 508, and a bottom wall 502. The first and second side walls504, 508, the end wall 506 and the bottom wall 502 cooperate to form ahousing-receiving region 540. The tray 500 may be thermal formed ormolded and is designed such that the housing 21 may be placed within thehousing-receiving region 540. One aspect of the tray 500 is that it canbe used as a catch-all if any litter or waste is kicked out of theself-cleaning litter box 20 by a cat.

Another aspect of the tray 500 is that it may be used to cooperate witha dome or hood 548 to define an enclosure 550 for the self-cleaninglitter box 20. The dome 548 may be used to provide privacy for the cat.The enclosure 550 includes a plurality of hood supports 530. The hoodsupports 530, may be metal or plastic strips. Each hood support 530 hasa first end portion 532 and a second end portion 534. To accommodate thehood supports 530, the first and second side walls 504, 508 have aplurality side of wall openings 510. The openings 510 are adapted toreceive the hood support end portions 532, 534.

The hood supports 530 are placed into the side wall openings 510 suchthat the end portions 532, 534 are retained therein by the resiliency ofthe hood supports 530 acting against the side walls 504, 508. The hood548 is placed over the hood supports 530 forming the enclosure 550. Thehood 548 has an opening 552 and may be made of cloth or any suitablematerial and may be connected to the hood supports 530 in any manner.For example, the hood supports 530 may be sewn into the hood 548.Alternatively, the hood 548 may have ties that connect the hood 548 tothe hood supports 530. Alternatively, the hood 548 can drape over thesupports 530 and attach to the sidewalls 504, 508.

FIG. 29 illustrates the waste receptacle 68 and its lid 69 in the closedcondition. There is a mass 271 of waste in receptacle 68, but thereceptacle is not yet full. Receptacle 68 is positioned in the litterbox 20 for engagement with bosses 222 and 223. The bosses 222 and 223extend inwardly from the litter box side walls 22, 23, respectively, toengage the indentations 63, 70 (FIG. 6). The walls of the wastereceptacle 68 adjacent side walls 22, 23 are provided with alignedopenings 226, 227, respectively. Radiation from a source 242 on wall 22impinges upon a detector 243 on wall 23 as long as the level of waste271 in the receptacle 68 does not block the radiation.

While the invention has been described in detail in connection withpreferred embodiments known at the time, it should be readily understoodthat the invention is not limited to such disclosed embodiments. Rather,the invention can be modified to incorporate any number of variations,alterations, substitutions or equivalent arrangements not heretoforedescribed, but which are commensurate with the spirit and scope of theinvention.

What is claimed as new and desired to be protected by Letters Patent ofthe United States is:
 1. A litter box, comprisinga housing for receivinglitter; a comb disposed in said housing; a motor for moving the combfrom the first position to a second position; and a sensor for sensingcontact by the comb with an obstruction as the comb is moved from thefirst position to the second position.
 2. The litter box of claim 1,wherein said sensor provides a shut-off signal when said sensor detectscontact with a cat.
 3. The litter box of claim 2, wherein said sensorincludes a switch coupled to said motor, said switch being movablebetween an open position and a closed position, the sensor providing theshut-off signal when the switch is in the closed position.
 4. The litterbox of claim 1, wherein said sensor includes a leaf switch.
 5. Thelitter box of claim 1, further comprising:a mode selector switch movablebetween a manual operation selecting position and an automatic operationselecting position; and a manual operation switch electrically connectedto said mode selector switch for driving said comb from said firstposition to said second position in response to actuation of said manualoperation switch when said mode selector switch is in the manualoperation selecting position.
 6. The litter box of claim 5, wherein saidmanual operation switch includes a foot pedal.
 7. The litter box ofclaim 1, further comprising a removable litter tray.
 8. The litter boxof claim 1, further comprising a replaceable waste receptacle.
 9. Thelitter box of claim 8, wherein said waste receptacle has a lid, andwherein said litter box further includes means for lifting said lid inresponse to movement of said comb.
 10. A self-cleaning cat litter box,comprising:a housing defining a litter chamber for receiving cat litter;a comb disposed in said litter chamber; a comb drive coupled to saidhousing, said comb drive including a drive motor; and a sensor coupledto the drive motor and positioned to detect contact with an obstruction,wherein the sensor generates a signal to change the state of said combin response to said contact.
 11. The cat litter box of claim 10, furthercomprising parallel side walls for preventing debris from spilling outof the cat litter box.
 12. The cat litter box of claim 10, wherein saidhousing is provided with rounded corners to facilitate cleaning, andwherein said litter chamber has no small spaces of the type which wouldpermit litter or waste to slip out of or become lodged in said box. 13.A self-cleaning cat litter box, comprising:a housing defining a litterchamber; a comb disposed in said housing; a comb drive coupled to saidhousing; a mode selector switch movable between a manual operationselecting position and an automatic operation selecting position, saidcomb drive driving said comb in response to a signal from a controllerwhen said mode selector switch is in the automatic operation selectingposition; and a manual operation switch electrically connected to saidmode selector switch, said comb drive driving said comb in response toactuation of said manual operation switch when said mode selector switchis in the manual operation selecting position.
 14. The self-cleaning catlitter box of claim 13, further comprising a housing access ramppivotally connected to said housing.
 15. The self-cleaning cat litterbox of claim 13, further comprising a tray having side walls and abottom wall that cooperate to define a housing-receiving region, aplurality of hood supports coupled to said tray, and a hood coupled tosaid supports, said hood having an opening.
 16. The self-cleaning catlitter box of claim 13, further comprising a removable litter tray forreceiving cat litter.
 17. A method of cleaning waste from a cat litterbox, comprising the steps of:operating said litter box according to amanual cleaning mode; subsequently, switching said litter box to anautomatic mode configuration; subsequently, operating said litter boxaccording to an automatic mode; and detecting an obstruction.
 18. Themethod of claim 17, further comprising the step of stopping the movementof a comb in response to detection of the obstruction.
 19. The method ofclaim 18, further comprising the step of reversing the direction ofmovement of the comb in response to detection of said obstruction. 20.The method of claim 17, further comprising the step of disablingoperation of said litter box for a predetermined period of time.
 21. Themethod of claim 20, further comprising the step of actuating anover-ride system to operate said litter box during said predeterminedperiod of time.